Preheat the oven to 200°C/400°F. Put the flour and baking powder into a bowl and rub in the cubes of butter, using your fingers until you have a mixture like coarse sand. Stir in the sugar. Refrigerate while you get on with the fruit.
Mix the cherries with the lemon zest, juice and sugar and divide among two 1-cup (240ml) capacity ovenproof ramekins.
Sprinkle the crumble topping over the fruit, place the ramekins in a baking sheet and bake for 20 minutes or until the topping is golden and the fruit is bubbling.